Preheat the oven to gas 4 / 180C / 350°F and line a brownie tin with baking paper
Mix all of the dry ingredients for the concrete into a bowl. Melt the butter then pour it into the dry ingredients and mix in - use your fingers to rub it together until it resembles a crumble topping mixture
Pour into the lined tin and push down with your hands until level. Bake for about 20 minutes or until it tests done. Remove from the oven and sprinkle the top with a little caster sugar. Mark out squares with a knife then gently slide the brownie still on the baking paper out of the tin onto a wire rack to cool
Combine the cornflour, sugar, food colouring and extract in a bowl. Add a little of the milk to make a paste. Pour the rest of the milk into a saucepan and gently heat until hot but not boiling
Once it's hot, pour into the pink paste, whisk to combine and then pour it all back into the saucepan. Keep stirring with the whisk until the mixture just comes to boil and thickens to a nice custard consistency, this won't take long. Once thickened remove from heat and pour over your chocolate concrete
We used to get this for pudding in the school canteen. The dinnerladies made the concrete so hard we would have competitions to see whose spoon bent the most trying to cut into it lol. The longer it rests, the harder it sets
